Interface floats in window after switching screen resolution
This seems to be a bug. This is considered off-topic on Blender Stack Exchange. 

See: What questions should be definitely off-topic?

Also this is to be expected since 2.80 version is not yet released and beta builds are still experimental. The bug should be reported: 



You should ensure that you are using up to date graphics drivers, which on Mac OS means you should run up to date OS(it seems yours is up to date already). Blender 2.80 builds are built daily as well, so you can check if the bug is fixed in later builds, but that has little chance of happening if it is not reported. 

Other than that, it seems Mac OS is not a perfect environment for doing 3d work at the moment. OpenGL support was dropped by Apple so if this by any chance is caused by a bug in their drivers, it is not going to be fixed in the future. I know it's not pleasant, but you may want to consider using another OS maybe in some sort of a dual boot set-up. It does not seem the situation with Mac OS is going to improve any time soon, it seems it might get worse.